The invention relates to a device for the blocking of a cylindrical inflow cross-section which is constructed between an interrupted interior wall of an exterior secondary duct and an interior engine circuit of a turbo fan ramjet engine.
Recently, combined turbine ramjet engines have been regaining importance, specifically within the framework of so-called "supersonic flight concepts" with an extremely high mission spectrum from take off to a high supersonic speed at high flying altitudes (up to an altitude of approximately 30 km). Among other concepts, the hypersonic flight concepts include a space flight equipment concept (Sanger Project) which, as will be described in the following, amounts to a two-stage concept. The first stage is to be carried by a flight apparatus which operates only within the atmosphere, while the second stage is based on a useful-load flight apparatus which is taken along in a "piggyback" manner by the mentioned flight apparatus. The useful-load flight apparatus, for use in space missions, has the purpose of continuing its assigned flight path on its own in the upper range of the atmosphere by way of a suitable rocket propulsion system. The flight apparatus responsible for the first stage must therefore be able to return, must be reusable, and carries out take offs and landings like a conventional airplane.
In the case of combined turbine ramjet engines which are to be used, for example, for a flight apparatus of this type, the turbojet engine must generally be switched off continuously, and the respective ramjet engine must be switched on continuously when a flying speed of approximately Mach 3 is reached in order to reach the desired high supersonic or hypersonic speeds of up to Mach 4.5 or even higher only by means of the ramjet engine. Flying speeds of approximately 2 Mach or even higher may be reached in this case in a combined operation of a"jet engine with a switched-on afterburner". The afterburner which is advantageously connected behind the jet engine part for this purpose and, as necessary, is acted upon by a combination of compressor or fan air and engine exhaust gas, may form the driving system for the ramjet operation by means of the connection of additional fuel injection devices, in addition to flame stabilizers, with a correspondingly apportioned exclusive supply of ambient air when the turbine jet engine part is disconnected.
For the mentioned uses, a combined fan ramjet engine has been suggested having a front fan driven by a basic engine comprising the gas generator, this front fan delivering air into a secondary duct sheathing of the basic engine and thus providing the main propulsive thrust in the subsonic operation. With a correspondingly adapted inlet and propelling nozzle geometry, in the case of the concerned engine, the basic engine with the fan must be switched off or shut down in the hypersonic operation, in which case, the exterior secondary duct will then be acted upon by the necessary ram air which, downstream of the basic engine end, is to be supplied to the supplementary combustion chamber for the ramjet operation.
In this connection, the required blocking devices or device of the basic engine part have a very special significance. In the blocking or locking position of the basic engine during ramjet operation, the basic engine must be impaired as little as possible by the comparatively high temperatures of the ram air (approximately 1,700 degrees C.). This also applies to the blocking devices proper which must be constructed to be correspondingly rugged and reliable. However, at the same time, they must ensure that, for example, in the subsonic operation, a perfect release is possible of the air supply from the fan into the exterior engine circuit (secondary duct) and into the internal engine circuit (basic engine) in correspondingly apportioned quantitative portions.
For this purpose, it may now be suggested to use centrally arranged as well as axially movable annular slides or swivel flaps which had become known in so-called "compound engine concepts" with variable power apportioning, with the purpose of selectively blocking or exposing, for example, a given interior-wall duct breakthrough as well as a, for example, annular inflow duct to the basic engine at the secondary duct--downstream of the fan. The annular slide concept, among other disadvantages, would have disadvantages with respect to relatively long axial adjusting paths as well as with respect to a relatively large installation volume which in many cases is not available for constructive reasons. A relatively large slide volume, in turn, would result in a comparatively high slide weight. The flap concept, among other disadvantages, would have the disadvantage of a relatively complicated construction which is susceptible to disturbances and requires a large amount of space, also with respect to the adjusting mechanism. The flaps, in this case, in a manner similar to propelling nozzles, would reach into or over one another in all positions--as a rotationally symmetrically close composite. Locally absolutely necessary sealing requirements and the mentioned temperature obstacles would also result in considerable technical implementation problems. The large number of different components which, in this case, results in a comparatively high susceptibility to disturbances which, in turn, make it impossible to exclude a comparatively high risk of foreign-body damage to the basic engine, particularly to the high-pressure compressor
In addition to the disadvantage of a comparatively high weight, an additional significant disadvantage of both concepts (annular slides or flaps) would be that, in each case, a blocking adjustment would have to take place in a relatively large-surface manner against an existing gas flow so that, in addition to a power-dominating, heavy construction, relatively high driving forces would also have to be applied to the adjustment.
It is an object of the invention to provide a blocking device of the initially mentioned type by means of which, while the construction is reliable, relatively simple and light-weight, a large-surface annular inflow cross-section can be blocked or exposed taking into account the relatively small available installation volumes in the engine.
According to the invention, this object is achieved by blocking device rings which are pushed into one another in an intermediate housing constructed as a flow divider, these rings being axially moved out of the intermediate housing by different distances with mutual surface contact, for the blocking of the inflow cross-section.
By means of utilizing a frequently existing intermediate housing section as a flow divider, the rings can securely be stored above one another and still provide a low length requirement for the installation. For blocking the inflow cross-section, the rings can therefore be axially moved with a relatively low aerodynamic resistance into a locally divided course of the existing compressed-air flow which results in a lighter design of the rings as well as in a relatively low adjusting power requirement.
Furthermore, a driving and adjusting device arrangement which is decentralized with respect to the engine may advantageously be provided, while utilizing ring-shaped installation volumes generally available at the engine side between the secondary and the primary circuit (secondary duct/basic engine).
The invention therefore, for example, offers the advantage that a blocking or closing device for the high-pressure compressor of the basic engine can be achieved without any unnecessary axial lengthening of the engine. The invention can therefore also be used advantageously when only extremely narrow space conditions are available in the engine.
The required displacement of the rings may be carried out by way of several actuating rod linkages which, at the rearward end, are connected to a ball roller spindle. In this case, the nuts of all ball roller spindles are disposed in gears which are connected by a flexible shaft existing along the whole circumference and are driven at one point. The driving may take place pneumatically, hydraulically or by means of an electric motor.
Since, during the same length of time, the closing rings must be moved out by different distances, the ball roller spindles for the respective interior and exterior ring are provided with different slopes.
The possibility also exists according to the invention to drive only the ring having the longest adjusting path and to pull along the respective other ring. For this purpose, the invention provides respective pull-along connecting devices which, in a very general sense, might be described as groove-and-tongue connections; i.e., pins or driving lugs are provided at the respective ring with the longest adjusting path, which can engage in correspondingly assigned axial grooves of the other ring which is to be pulled along.
As a further development of the basic idea of the invention, the respective actuating rod linkages or the compression-tension rods may be sealingly guided in the area of penetration at the intermediate housing wall, so that occurring leakage air can only reach the corresponding interior branch duct of the basic engine.
The ring construction of the blocking device according to the invention is characterized by a small number of components so that the risk of susceptibility to disturbances is low and there is also no danger that component breakages or the like may occur which may have the result that fragments may fly into the high-pressure compressor of the basic engine.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.